The bordello Aux Belles Poules, The Cute Chicks, at 32, Rue Blondel. The alleyway runs off the Rue St. Denis, which has been Paris' main thoroughfare for illicit sex since the Middle Ages—"the Champs-Élysées of prostitution."

The Hotel Édouard VII on the Avenue de l'Opéra. For over a quarter of a century, the building housed the private apartment of the Prince of Wales, the future King Edward VII, who enjoyed the pleasures of belle époque Paris to the full.

The legendary fauteuil d'amour, the "sex chair" of King Edward VII, photographed in 1951, before it disappeared into private hands. "Dirty Bertie" had the device built so that he would not crush prostitutes with his enormous bulk.

The courtesans' mirror in the private dining room upstairs in Restaurant Lapérouse on the Left Bank. The filles de joie would test their diamonds on the glass to make sure they weren't being short-changed by gentlemen for their favors.

The monumental bed of courtesan La Valtesse de la Bigne, now on proud display in the Museum of Decorative Arts, part of the Louvre. La Valtesse had risen from poverty to become the lover of Emperor Napoleon III and an influence on his diplomatic decisions. Her bed cost the equivalent of $400,000 when it was built in 1875 and quickly became the talk of Paris. Émile Zola, who visited her mansion, describes it in his novel Nana as "an altar, to which all of Paris would come to adore [the courtesan's] sovereign nudity"—but he was obliged to invent the details of the decorations. Despite his pleas, La Valtesse refused to let him inspect the inner sanctum of her bedroom. ("Chasse gardée, maître," she reportedly laughed. "Private hunting ground, maestro.")

The Hôtel La Païva, the last of the grand courtesans' houses on the Champs-Élysées, which once sat cheek by jowl with the mansions of France's politicians and millionaires. The palace belonged to La Païva, a steel-willed, Russian-born beauty whose real name was Esther Lachmann and who became the lover of composer Richard Wagner, among others. It escaped demolition in the 20th century by thriving as a private English club. Today, the mansion's basement has been turned into a sepulchral restaurant, called (of course) La Païva, swathed in velvet drapes, its banquettes framed by columns evoking the classical caryatids of the Acropolis.

The entrance staircase of No. 12 Rue Chabanais, once the most luxurious brothel in Europe. The lobby was designed as a magical underground grotto, complete with flowing waterfall and a sign that said, "WELCOME TO LE CHABANAIS, HOUSE OF ALL NATIONS." (Tellingly, the sign was in English.)

The Louis XV Room of Le Chabanais. The brothel was known for its "fantasy chambers" catering to every taste. Clients could choose between the Pompeii Room, the Japanese Room, the Louis XV Room, the Eskimo Room, the Pirate Room, and others. "Dirty Bertie" (the Prince of Wales) favored the Hindu Room.

The exterior of No. 12 Rue Chabanais today. In 1946, all the brothels of Paris were closed, ending nearly a century and a half of tolerance. Le Chabanais was converted into housing for foreign students.

Marthe Richard, who led the campaign to have the brothels closed in 1946. Presenting herself as a hero of the French Resistance, she was later exposed as a fraud—a former prostitute and collaborator who had supplied women to the Nazis.

The interior of No. 12 Rue Chabanais today. The staircase is original, as are the elevators. There were two synchronized elevators, one ascending while the other descended, so that clients wouldn't be embarrassed by accidental meetings.

Louis Soubrier, whose great-grandfather manufactured the royal "sex chair" for the use of the Prince of Wales in the fantasy brothel Le Chabanais. The family firm now deals in antiques, renting out many pieces for films.

The legendary "sex chair" of King Edward VII in its current Parisian home on the top floor of the Soubrier warehouse. It was created for use in the Hindu Room of the brothel so that the obese "Dirty Bertie" would not crush prostitutes with his massive bulk.

An artist's recreation of how the sex chair was used. According to legend, the device allowed the Prince of Wales to sleep with two women at once—although "the precise arrangement," the current owner says delicately, "is open to debate."